Marine environment is rich in microbial resources, which can provide range of novel bioactive compounds like enzymes, secondary metabolites etc. It has also remarkable bioremediation capabilities. Study of marine bacteria is important as they play a crucial role in decomposition of organic matter and cycling of nutrients. But our knowledge of marine bacterial diversity is critically limited. In addition to that, pollution monitoring of seawater with respect to bacterial diversity is very important to understand its quality. It is a challenging task to isolate maximum types of bacteria from these water samples as bacterial concentration in the seawater as well as other sources are very low. In addition to that depth wise bacterial diversity study of marine water is very important. In general, the depth-related gradient of physical and chemical properties provides niches for a wide variety of metabolically diverse microorganisms in marine water. Bacterial distribution in the marine water is not uniform throughout different water depths. Factors affecting this distribution are carbon, nitrogen, phosphorous limitations, temperature, light, pressure and salinity etc. At air-water interface of seawater, bacterial concentration is more and it decreases as depth increases. Hence, there bacterial diversity profiling of different seawater depth is important.
In general filtration is a common method to concentrate the bacteria before plating. However, during filtration process, small size bacteria can escape through the filter and also the barophobic bacteria might get damaged during this process. Therefore majority of the time when diversity study is performed with filtration method, many species do not appear in the result. Further, water sample generally collect for bacterial diversity study comprises small volume which might not represent all the types of bacteria. Various materials viz. ceramic, polymers are used for the preparation of these membranes. However, the simplicity in preparation in cost effective manner using particular type of membrane is very difficult. There are many kinds of bacteria which have been recovered from different membranes.
Reference may be made to a patent CN101864386A, wherein it describes a method for enriching seawater bacteria by asepsis cellulose filter membrane. This enrichment method uses sterilized syringe and a syringe needle type filter. The asepsis cellulose filter membrane is put in a sterilized filer and seawater is filled into the filter by the syringe and enriching seawater bacteria. The cellulose filter membrane enriched with seawater bacteria is kept on a culture medium and cultivated subsequently. In this patent external efforts are needed to collect the bacteria.
Reference may be made to a patent CN102175632A, wherein it describes a bacterial detection method, which comprises a sampling method in which the test sample is passed through a hollow fiber filtration unit for trapping bacteria and/or bacterial metabolites in hollow fiber membranes which get accumulated in the filter unit. Again the sampling method is filtration based. Using this method, certain types bacteria may be missed which cannot withstand applied pressure or can pass through the pore of the membrane.
Reference may be made to an existing techniques which is used to collect samples of seawater involve immersing an open ended tube, like a Niskin bottle, to the required depth and then manually triggering spring-loaded caps at both ends of the tube, to close the tube and capture the sample. The tube is typically let down into the sea at the end of a line and, when the required depth is reached, a weight (messenger) is dropped down the line to trigger closure. The closed tube can then be drawn back and the seawater sample transferred to a flask for analysis. The open end of the glass tube is not sealed; therefore there is a chance of both water and atmospheric contamination. In addition to that, containers used for that purpose is of massive size to withstand pressure differential between an evacuated container and the ambient water pressure which are needed for great depths. Sterilization of the containers is very difficult.
It is therefore an object of the present invention to provide improved underwater sampling device and methods.